The present invention relates to an optical element array, including a lens sheet that uses a lenticular lens or a fly-eye lens to provide image display to a plurality of view points, for providing a unique display such as a stereoscopic display and view angle control; a display device; and a method of manufacturing a display device, an optical element array and an optical element array molding die.
With the need for a more sophisticated display device in recent years, a unique display device that combines an optical element array such as lenticular lens, prism sheet, or diffusion sheet to a display panel which uses electrical optical element such as liquid crystal, and that enables a stereoscopic image display and view angle control is used.
A display device using a lenticular lens sheet will be described by way of example of such display device. FIG. 16 is a frame format perspective view of the lenticular lens sheet, and FIG. 17 is a frame format view showing a configuration example of the display device using the lenticular lens sheet and a stereoscopic display method.
As shown in FIG. 16, a lenticular lens sheet 110 has one surface that is planar, and the other surface that is arranged with a plurality of cylindrical lenses 111 continuously in the parallel direction, each cylindrical lens having a hog-backed cross section at a circular cylindrical surface.
As shown in FIG. 17, a left eye pixel 115a and a right eye pixel 115b are alternately arranged so as to correspond to the focus of each cylindrical lens 111 on a display panel 114. When the left eye pixel 115a and the right eye pixel 115b are driven according to a predetermined signal by a drive circuit (not shown), a left eye image is formed in a left eye region 120a and a right eye image is formed in a right eye region 120b by the cylindrical lens 111, and a stereoscopic image is recognized by the observer. A normal two-dimensional image display can also be obtained by driving the right eye pixel 115a and the left eye pixel 115b with the same signal.
A multi-image simultaneous display device for displaying multiple images simultaneously has been proposed as a display device using the lenticular lens sheet. This device also enables simultaneous display of different images to a plurality of observers by allocating the image in observing directions by the cylindrical lens with a method similar to that for the stereoscopic display as described above.
In such display device using the lenticular lens sheet, the lenticular lens sheet is required to be mounted on the display panel at high precision to obtain a high quality stereoscopic image display or a multi-image simultaneous display. A technique proposed in Japanese Laid-Open Patent Publication No. 6-324317 (P. 3, [0013] to [0018], FIG. 1) (patent document 1) for such problem is shown in FIG. 18.
FIGS. 18A, 18B, 18C and 18D are frame format views describing a basic configuration of the invention of patent document 1, where 18A is a frame format view of a display panel, 18B is a frame format view of a lenticular lens plate and an alignment lenticular lens, 18C is a frame format view of a state in which the lenticular lens plate is slanted and overlapped with respect to the display panel, and 18D is a frame format view of when the lenticular lens plate is accurately overlapped.
A configuration in which a linear alignment mark 213 is arranged on one side of a display region 212 of the display panel 211, and an alignment lenticular lens 215 is arranged at a position corresponding to the alignment mark 213 of the lenticular lens plate 214 is proposed. According to such configuration, when the lenticular lens plate 214 is rotation shifted with respect to the display panel 211, only one part of the linear alignment mark 213 is enlarged as shown in FIG. 18C, and thus alignment can be easily carried out by moving the lenticular lens plate 214 such that the entire linear alignment mark 213 is enlarged as shown in FIG. 18D.
Similar technique is also proposed in Japanese Laid-Open Patent Publication No. 10-123633 (P. 3, [0016] to [0023], FIG. 1) (patent document 2). FIGS. 19A and 19B are frame format views describing a basic configuration of the invention of patent document 2, where 19A is a frame format view of a lenticular lens plate and 19B is a frame format view of an image sheet; and FIGS. 20A and 20B are frame format views in which parts of FIGS. 19A and 19B are enlarged, where 20A is a partial cross sectional view of the lenticular lens plate and the image sheet and 20B is a partial top view of the image sheet.
In this configuration as well, a reference line 317 is formed on the image sheet 315, and a positioning groove 314 is formed in the lenticular lens plate 312 at a position corresponding to the reference line 317, where adjustment is made such that the reference line 317 can be clearly observed as one straight line through the groove 314.
However, the background art described above has the following problems. The techniques disclosed in patent document 1 and patent document 2 of arranging a linear reference mark in the display panel and forming the lenticular lens or the groove at a position corresponding to the reference mark of the lenticular lens sheet to be mounted on the display panel is advantageous when performing alignment at visual level. However, with higher definition of the recent display panel, there are limitations to mounting precision in the technique of observing the reference mark through the lenticular lens or through the groove when higher precision mounting of the lenticular lens is being demanded.
One example of such case is shown in FIGS. 21A and 21B. FIGS. 21A and 21B are frame format views describing production of error when observing the reference mark through the lenticular lens, where 21A is a frame format view of the reference mark arranged on the display panel and 21B is a frame format view when observing the reference mark through the lenticular lens.
When observing the reference mark 130 arranged on the display panel (not shown) without interposing the lens, the reference mark appears as a straight line as shown in FIG. 21A. The state of FIG. 21B is obtained when observed with the lenticular lens 110 interposed on the reference mark 130 but without the lenticular lens 110 interposed on one part of the reference mark 130. A difference of ΔL is created when observed through the lens. The dimension of ΔL changes with lens specification such as lens shape and refraction index of lens material, and also changes with respect to the reference mark imaging position shift (change with respect to normal line direction from the reference mark). Therefore, high precision alignment through the lens is very difficult.
Problems still arise even if a groove pattern is used as shown in FIGS. 20A and 20B. FIGS. 22A and 22B are frame format views of when observing the reference pattern through the groove when the groove pattern is used for the lens, where 22A shows interference of the bottom part of the groove and the reference line and 22B shows lowering in visibility of the reference line caused by the groove shape and the refraction index of the groove material.
First, the groove bottom part 131 interferes with the reference line 317 thereby inhibiting the high precision alignment, as shown in FIG. 22A. Secondly, the visibility of the reference line 317 lowers due to the groove shape and the refraction index of the groove material when performing alignment using transmissive light 132, as shown in FIG. 22B.
The alignment precision further lowers since the pitch precision, the shape precision (curvature precision for lenses), or the like of the positioning lenticular lens or groove pattern varies.
In recent display panels, a display panel incorporating a drive circuit such as a gate driver circuit using a system-on-glass technique on the outer side of the display part region is proposed. When applying the method of known technique of arranging a linear reference mark in the display panel with respect to such display panel, a response such as arranging the reference mark on the outer side of the drive circuit and the like is required, and thus the frame becomes extremely large.